Process for bulk dyeing of plastics

ABSTRACT

A process for bulk dyeing of plastics comprising the step of adding a dye of the formula (I)  
                 
 
     wherein  
     Y is a bivalent radical selected from the group consisting of substituted and unsubstituted arylenes and alkylenes, and substituted and unsubstituted alkylene radicals interrupted in the main chain by heteroatoms such as O or S,  
     R 1  and R 1 ′, independently of one another, are an electron-withdrawing group,  
     R 2 , R 2 ′, R 3  and R 3 ′, independently of one another are hydrogen, alkyl,  
     R 4  and R 4 ′, independently of one another, are unsubstituted or substituted alkyl.  
     to plastic.

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The invention relates to a process for bulk dyeing of plastics with dyes of the formula (I).

[0002] The plastic industry is always searching for new dyes and colorings that have good light resistance, good weathering resistance, and heat resistance, especially in the thermoplastics field.

SUMMARY OF THE INVENTION

[0003] The invention relates to a process for bulk dyeing of plastics comprising the step of adding a dye of the formula (I).

[0004] wherein

[0005] Y is a bivalent radical selected from the group consisting of substituted and unsubstituted arylenes and alkylenes, and substituted and unsubstituted alkylene radicals interrupted in the main chain by heteroatoms, such as O or S,

[0006] R¹ and R¹′, independently of one another, are an electron-withdrawing group, preferably cyano or alkoxycarbonyl, in particular C₁-C₄-alkoxycarbonyl,

[0007] R², R²′, R³ and R³, independently of one another are hydrogen, alkyl, in particular C₁-C₄-alkyl, CF₃ or halogen, preferably F or Cl,

[0008] R⁴ and R⁴, independently of one another, are unsubstituted or substituted alkyl, preferably C₁-C₆-aIkyl, or C₇-C₁₂-aralkyl, preferably benzyl. to plastic.

[0009] Examples of preferred radicals Y include unsubstituted or substituted phenylene, or unsubstituted or substituted C₁-C₆-alkylene.

[0010] Examples of more preferred radicals Y include: 1,3-phenylene, 1,4-phenylene or methyl-substituted 1,3- or 1,4-phenylene, —CH₂—CH₂—, —CH₂CH₂CH₂—, —(CH₂)₄—, —CH₂CH(CH₃)—, —CH₂CH₂—O—CH₂CH₂— and —CH₂CH₂—S—CH₂CH₂—.

[0011] Examples of most preferred radicals Y are alkylene radicals, in particular —CH₂CH₂—, —(CH₂)₃—, —(CH₂)₄—, and —CH₂CH₂—O—CH₂CH₂—.

[0012] Examples of preferred radicals R¹ and R¹′ include: —CN, —CO₂CH₃, —CO₂CH₂CH₃, —CO₂(CH₂)₂CH₃ and —CO₂(CH₂)₃CH₃.

[0013] Examples of preferred radicals R², R²′, R³ and R³ include hydrogen, methyl, ethyl, Cl, F, CF₃, methoxy and ethoxy.

[0014] Examples of preferred radicals R⁴ and R⁴′ include CH₃, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl.

[0015] In one preferred embodiment the radicals R¹═R¹, R²═R²′, R³═R³ and R⁴═R⁴′ are equal in formula (I).

[0016] It is particularly preferable to use dyes of the formula (la)

[0017] wherein

[0018] Y is unsubstituted or substituted phenylene, in particular 1,3- or 1,4-phenylene, or unsubstituted or substituted C₂-C₆-alkylene, in particular ethylene, propylene or butylene,

[0019] R¹ is CN, CO₂CH₃, CO₂CH₂CH₃ or CO₂(CH₂)₃CH₃,

[0020] R² is hydrogen, CH₃ or CH₂CH₃, and

[0021] R⁴ is CH₃, CH₂CH₃, n-propyl or n-butyl.

[0022] Preference is likewise given to the use of dyes of the formula (I) wherein at least one of the substituent pairs R¹/R¹, R²/R²′, R³/R³′ and R⁴/R⁴′ is non-identical (e.g.. R¹≠R¹′). These asymmetric dyes of the formula (i) are also included in this invention.

[0023] Bulk dyeing, for the purposes of this application, is in particular any process in which the dye of the formula (I) is incorporated into the molten plastic material, including with the aid of an extruder, or in which the dye is added to the starting materials in the preparation of the plastic, e.g., to the monomers, prior to polymerization.

[0024] The approximate processing temperatures for bulk dyeing are from 100 to 380° C.

[0025] Some of the dyes to be used according to the invention are known (e.g., CH-516 628, JP-A 02 292 371), and others may be prepared by analogy with processes known from the literature. An example of a preparation is a Vilsmeier formulation followed by condensation with a reactive methylene compound, preferably malononitrile.

[0026] A preferred preparation is the condensation of a substituted aniline with a dihalogenoalkylene (Eq. 1)

[0027] wherein

[0028] n is from 2 to 6, and

[0029] X represents halogen, in particular Cl or Br, and the other substituents are as defined above,

[0030] or condensation of a substituted aniline with an N-(halogenoalkyl)aniline (Eq. 2), for example in a solvent or in bulk, in the presence of a base, followed by Vilsmeier formulation (preferably by reacting with POCl₃ and dimethylformamide, followed by hydrolysis), followed by condensation with a reactive methylene compound, preferably malononitrile.

[0031] Examples of suitable thermoplastics include: cellulose esters (such as cellulose nitrate, cellulose acetate, cellulose triacetate, cellulose acetobutyrate and cellulose propionate), cellulose ethers (such as methylcellulose, ethylcellulose and benzylcellulose), linear saturated polyester resins, aniline resins, polycarbonates, polystyrene, polyvinylcarbazole, polyvinyl chloride (in particular unplasticized PVC), polymethacrylates, polyvinylidene chloride, polyacrylonitrile, polyoxymethylenes, linear polyurethanes. Examples also include copolymers (such as vinyl chloride-vinyl acetate copolymers), and in particular styrene copolymers (such as styrene-acrylonitrile copolymers (SAN), styrene-butadiene copolymers (SB) and styrene-α-methylstyrene copolymers (SMS) and acrylonitrile-butadiene-styrene copolymers (ABS).

[0032] The high-molecular-weight compounds mentioned may be present individually or in mixtures, as plastic materials or melts, which may be spun to give fibres, if desired.

[0033] The novel process is particularly suitable for bulk dyeing of polystyrene, and in particular for bulk dyeing of poly(meth)acrylates, and preferably polymethyl methacrylate SAN, SMS, ABS, or else polyethylene terephthalate or polybutylene terephthalate.

[0034] The plastic to be dyed is preferably in the form of powders, chips or pellets and is to be mixed intimately with the dye. One method of achieving this is by coating the plastic particles with the finely divided, dry, pulverulent dye, or by treating the particles with a solution or dispersion of the dye in an organic solvent and then removing the solvent.

[0035] The process of the invention may also use mixtures of different dyes of the formula (I) and/or mixtures of dyes of the formula (I) with other dyes and/or with inorganic or organic pigments.

[0036] The dyes of the formula (I) are preferably in their solid form, in particular pulverulent or granular, when used according to the invention.

[0037] These solid dye preparations contain at least 95% by weight, preferably at least 98% by weight, in particular more than 99% by weight, of dye of the formula (I) and, if desired, up to 5% by weight of organic binder, in each case based on the dye preparation.

[0038] These solid dye preparations are also within the scope of the invention.

[0039] Examples of possible binders are ethylene oxide-propylene oxide block copolymers, preferably those with a molar mass of from 4000 to 16,000 g/mol.

[0040] When used for dyeing, the dye preparations are preferably in the form of powders, in particular in the form of dry powders which have been ground and meshed, or else are in the form of pellets, such as those prepared in accordance with EP-A-488 933.

[0041] The ratio of dye to plastic can vary within wide limits, depending on the desired color strength. It is generally advisable to use from 0.005 to 5% by weight, preferably from 0.01 to 2% by weight, of dye, based on the amount of the plastic to be dyed.

[0042] High-quality opaque colorings can be obtained by adding pigments insoluble in the polymers or the polymer/dye mixtures, e.g., titanium dioxide.

[0043] Examples of the amounts of titanium dioxide which can be used are from 0.01 to 10% by weight, preferably from 0.1 to 5% by weight, based on the amount of polymer.

[0044] The treated polymer particles are melted by known processes in an extruder and extruded to give articles such as films or fibres, or cast to give sheets.

[0045] One way of dyeing the plastics with the dyes of the formula (I) is to admix a dye of this type, if desired in the form of a masterbatch, with these substrates using roll mills, mixing equipment or grinding equipment. The dyed material is then brought into its final form by known processes, including calandering, compression molding, extruding, spreading, casting or injection molding.

[0046] It is often desirable to incorporate plasticizers into the high-molecular-weight compounds prior to shaping, in order to produce non-rigid moldings or to reduce the brittleness of the same. Suitable plasticizers include esters of phosphoric acid, phthalic acid or sebacic acid. In the process of the invention, the plasticizers may be incorporated prior to or after the incorporation of the dye into the polymers. It is also possible to add any desired amounts of fillers and/or other coloring constituents, such as white pigments, color pigments or black pigments, in order to achieve different shades.

[0047] The resultant greenish-to reddish-yellow colorings have good light resistance and good weathering resistance. The dyes of the invention are also very heat-fast within the thermoplastics.

[0048] The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.

EXAMPLE 1

[0049] 0.1 g of the dye of the formula

[0050] and 2 g of titanium dioxide (Bayertitan R-FK-2, Bayer AG), and 100 g of a pelletized polystyrene were mixed for 2 hours in a sealed container on a roller bed. The resultant mixture was extruded at about 230° C. to extrudates of width 2 cm and repelletized. The pellets were injection molded at from 230 to 240° C. This gave reddish-yellow-colored moldings with high light resistance and high brilliance.

EXAMPLE 2

[0051] 0.02 g of the dye of the formula (A) and 100 g of a pelletized polystyrene were mixed for 2 hours in a sealed container on a roller bed. The resultant mixture was then injection molded at from 230° C. to 240° C., using an injection-molding machine with a screw, to give moldings. The yellow-colored, transparent moldings had high lightfastness.

EXAMPLE 3

[0052] If the dye of the formula (I) was replaced by the dye of the formula (B)

[0053] and the procedure was otherwise as in Example 1, yellow-colored moldings with high lightfastness were obtained.

EXAMPLE 4

[0054] If 0.035 g of the dye of the formula (B) and 100 g of a pelletized polystyrene were mixed and the procedure was otherwise as described in Example 2, yellow-colored, transparent moldings with high lightfastness were obtained.

EXAMPLE 5

[0055] 0.03 g of dye of the formula (A) were dissolved in 99.97 g of methyl methacrylate. After addition of 0.01 g of dibenzoyl peroxide the solution was heated to 120° C. and the polymerization initiated. After 30 minutes, the methyl methacrylate which had begun to polymerize was placed between two glass plates and the polymerization completed for 10 hours at 80° C. This gave yellow-colored, transparent polymethyl methacrylate sheets.

EXAMPLE 6

[0056] 0.02 g of dye of the formula (B) and 100 g of polymethyl methacrylate were mixed dry and homogenized in a twin-screw extruder at 240° C. The material discharged as extrudate was pelletized. It was then shaped by press-molding. This gave a transparent, yellow-colored plastic with very good lightfastness and weather fastness.

EXAMPLE 7

[0057] 100 g of a commercially available polycarbonate in the form of pellets were mixed dry with 0.01 g of solid of the formula (A). The resultant pellets were homogenized in a twin-screw extruder at 350° C. This gave a transparent, yellow coloration with good lightfastness. The dyed polycarbonate was discharged as extrudate and pelletized.

EXAMPLE 8

[0058] 0.04 g of solid of the formula (B) were mixed dry with 100 g of styrene-acrylonitrile copolymer and homogenized in a twin-screw extruder at 190° C. and pelletized. Shaping the pellets by press-molding gave a transparent, colored plastic with good lightfastness. If 1% of titanium dioxide was added during the operation an opaque coloration was obtained.

EXAMPLE 9

[0059] If in Example 1 the dye of the formula (A) was replaced by the dye of the formula

[0060] and the procedure of Example 1 was repeated, yellow-colored moldings with good lightfastness were obtained.

EXAMPLE 10 TO 15

[0061] The following dyes may be used instead of the dyes of the formulae A, B and C in Examples 1 to 9, with similar substances:

[0062] Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims. 

What is claimed is:
 1. A process for bulk dyeing of plastics comprising the step of adding a dye of the formula (I)

wherein Y is a bivalent radical selected from the group consisting of substituted and unsubstituted arylenes and alkylenes, and substituted and unsubstituted alkylene radicals interrupted in the main chain by heteroatoms such as O or S, R¹ and R¹′, independently of one another, are an electron-withdrawing group, R², R²′, R³ and R³′, independently of one another are hydrogen, alkyl, R⁴ and R⁴′, independently of one another, are unsubstituted or substituted alkyl. to plastic.
 2. The process of claim 1 , wherein R¹ and R¹′, independently of one another, are cyano or alkoxycarbonyl.
 3. The process of claim 2 , wherein the alkoxycarbonyl is C₁-C₄-alkoxycarbonyl.
 4. The process of claim 1 , wherein R², R²′, R³ and R³′ are independently of one another are C₁-C₄-alkyl, CF₃ or halogen.
 5. The process of claim 4 , wherein the halogen is F or Cl,
 6. The process of claim 1 , wherein R⁴ and R⁴′, independently of one another, are unsubstituted or substituted C₁-C₆-alkyl, or C₇-C₁₂-aralkyl.
 7. The process of claim 6 , wherein R⁴ and R⁴′ are benzyl.
 8. The process of claim 1 , wherein Y is selected from the group consisting of 1,3-phenylene, 1,4-phenylene, methyl-substituted 1,3- or 1,4-phenylene, unsubstituted or substituted C₂-C₆-alkylene.
 9. The process of claim 1 , wherein the unsubstituted or substituted C₂-C₆-alkylene, is —CH₂—CH₂—, —CH₂CH₂CH₂—, —(CH₂)₄—, —CH₂CH(CH₃)—, —CH₂CH₂OCH₂CH₂- or —CH₂CH-S—CH₂CH₂—.
 10. The process of claim 1 , wherein R¹ and R¹′, independently of one another, are CN, CO₂CH₃, CO₂CH₂CH₃, —CO₂(CH₂)₂CH₃ or CO₂(CH₂)₃CH₃.
 11. The process of claim 1 , wherein R², R²′, R³ and R³′, independently of one another, are hydrogen, methyl, ethyl, Cl, F or CF₃.
 12. The process of claim 1 , wherein R⁴ and R⁴ are CH₃, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl.
 13. The process of claim 1 , wherein R¹ R¹′, R²═R²′, R³═R³′ and R⁴═R⁴′.
 14. The process of claim 1 , wherein the dyes is of the formula (Ia)

wherein Y is 1,3- phenylene, 1,4-phenylene, ethylene, propylene or butylene, R¹ is CN, CO₂CH₃, CO₂CH₂CH₃ or CO₂(CH₂)₃CH₃, R² is hydrogen, CH₃ or CH₂CH₃, and R⁴ is CH₃, CH₂CH₃, n-propyl or n-butyl.
 15. The process of claim 1 , wherein at least one of the substituent pairs R¹/R¹′, R²/R²′, R³/R³ and/or R⁴/R⁴′ is non-identical.
 16. The process of claim 1 , wherein the dye is (A) or (B):


17. A compound of the formula

wherein Y is a bivalent radical selected from the group consisting of substituted and unsubstituted arylenes and alkylenes, and substituted and unsubstituted alkylene radicals interrupted in the main chain by heteroatoms such as O or S, R¹ and R¹′, independently of one another, are an electron-withdrawing group, R², R²′, R³ and R³′, independently of one another are hydrogen, alkyl, R⁴ and R⁴′, independently of one another, are unsubstituted or substituted alkyl and wherein at least one of the substituent pairs R¹/R¹′, R²/R²′, R³/R³′ and/or R⁴/R⁴′ is non-identical.
 18. A solid dye preparation comprising at least 95% by weight of a dye of the formula (I) according to claim 1 .
 19. A process for preparing dyes according to claim 17 , wherein a substituted aniline is reacted with a dihalogenoalkylene

wherein n is from 2 to 6, X is halogen, in particular Br or Cl, and the other substituents are as defined above, or a substituted aniline is reacted with an N-(halogenoalkyl)aniline (Eq. 2), for example in a solvent or in bulk in the presence of a base, followed by a Vilsmeier formulation (preferably by reacting with POCl₃ and dimethylformamide, followed by hydrolysis) followed by condensation with a reactive methylene compound, preferably malononitrile.
 20. Copolymer from the group consisting of styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS), dyed with at least one dye of the formula (I) according to claim 1 . 